Brushless DC motor having opposed pairs of axial magnetic field type permanent magnets and control system therefor

Abstract

A brushless DC motor includes opposed pairs of axial magnetic field type permanent-magnets. Two opposed stators are axially arranged at two opposite sides of a rotor, each and stator includes a plurality of equiangularly spaced electromagnetic zones and in least one winding at each electromagnetic zone. A control system is provided to detect phase angle and the revolving speed of the rotor through a sensor and to control the connection of DC current to each winding and its direction, enabling the windings in the electromagnetic zones to form with the rotor at least one motor. By means of detecting speed change of the rotor through the sensor, the control system controls the opposed pairs of axial magnetic field type permanent-magnet brushless DC motor to operate under different motor operation combinations and to output different torques.

What the invention claimed is: 
     
       1. A brushless DC motor comprising: a rotor having an axis and a plurality of permanent magnets equiangularly spaced around a center of the rotor, each of said magnets having poles arranged in an axial direction parallel to said axis, respective poles of each adjacent two of said permanent magnets having a reversed polarity;   two opposed stators disposed on two opposite sides of said rotor in said axial direction, said stators each comprising a plurality of equiangularly spaced electromagnetic zones respectively facing said rotor, said electromagnetic zones each comprising an iron core supporting one concentrated winding; and   a control system arranged to selectively connect and disconnect each of the windings to a source of DC current and to control a direction of the DC current supplied to each of the windings in the electromagnetic zones, said selective connection and disconnection of the windings, and said direction of DC current in said each of the windings, determining at least one property of motor, said control system comprising at least one sensor to detect a phase angle and revolving speed of said rotor;   wherein said control system controls the selective connection or disconnection, and the direction of a DC current supplied to different combinations of said concentrated windings based on detection of speed changes or of said rotor through said sensor to cause said brushless DC motor to have different properties and to output different torques.   
     
     
       2. The brushless DC motor of claim 1, wherein said control system is a DC control system with a three-phase 6-wire bridge circuit. 
     
     
       3. The brushless DC motor of claim 1, wherein said control system is an electronic phase-changing control system. 
     
     
       4. The brushless DC motor of claim 1, wherein said sensor comprises at least one Hall sensor.